A voluntary associa



E. D. TILLYER OPHTHALMIC LENS Sept 17, 1929.

Original Filed Mardh 9, 1927 I Line 0 direcfvision Lm: or nmzcr VISION Prmr nri jupflcnl cenTer aul..

. I 3044142144? 5:15am Q'Tfillge? Reissued Sept 17, 1929 UNITED STATES PATENT OFFICE EDGlkfl D. TIIJLYER, OF SOUTHBRIDGE, MASSACHUSETTS, ASSIGNOR TO ERICLN OPTICAL COMPANY, OF SOUTHBRIDGE, MASSACHUSETTS, A VOLUNTARY ASSOCIA- TION MASSACHUSETTS Original No. 1,697,030, dated January 1 This invention relates to improvements in ophthalmic lenses and mountings for the same and has particular reference to an improved opthalmic lens and mounting for the same to be used in goggles for aviators, autoists and the like.

The principal object of the invention is to reduce the oblique astigmatism and prismatic deviation usual in devices of this character.

Another object of the invention is to provide a lens for a device of this character which is designed from the centerof rotation of the eye togive the best vision throughout the useful range of vision of the eye.

Another object of the invention is to provide alens for a device of this character that will give the best average vision throughout therange of vision of the lens.

Another object of the invention is to pro vide a lens for a device of this character that will have sensibly no power at a position straight in front of the eye.

Another object of the invention is to provide a device of this character that will pro vide binocular vision without eye strain resulting from extraneous prismatic action present in the prior art devices.

Another object of the invention is to provide in-a device of this kind an optically designed lens in contra-distinction to nonoptical lenses hitherto used for analogous purpose.

Other objects and advantages of the inven tion will be apparent from the following description. taken in connection with the accompanying drawingsand it is apparent that many changes may he made in the details of construction and arrangements of parts without depn rting from the spirlt of theinvention as set forth inthe accompanying claims. I tlu 1fet'o1'c,, do not wish to beli'mited to the cxactdciails of construction and arrange ments shown. the preferred forms only ha ing been shown by way of illustration.,.]

Referring to the drawings:

Fig. l is a diagrammatic cross sectional view of the lens of the invention showing the optical determination of same;

. Fig. i! is a cross section through the lenses and lens inountin of a og le in nosition OPHTHALMIC LENS Serial No. 173,879, filed March 9, 1927. Application for reissue filed July 15, 1929.

that a curved lens having concentric faces about the same center will produce a lens concave in power, that the lens instead of having no power will have a minus power and also that a lens wherein the two faces have the same radiusof curvature will have a positive power. It is also Well known that somewhere in between these two forms there exists a lens having neither positive nor negative power along the axis of this lens, i. e., the line. connecting the two centers of curvature. This axis'in the prior art lenses has been placed near the geometrical center of the lens that is at a point A of the drawings. In wearing this goggle as in Fig. 2 it is apparent that this optical axis is notused for binocular vision in its usual fields but the part of the lens nearer the nose is the part that is usually used for this purpose. In the prior art lenses the optical aberrations as the lenses are worn are very large in this custom ary binocular field of useful vision.

In the lens of the invention the radii of the surfacesare computed to give a zero optical power and the optical center in front of the eye or at B, Fig. 1 and'with a definite the errors of vision where there is binocular I VlSlOn will .be double, that is, those ofone side lus' those of the other and where there is on y monocular vision each lens has the single vision of that particular type; in other words, the errors for binocular vision are doubled and those for monocular vision are not.

matic aberration in cases of this kind is ap- HAIR. 0.00 mowers. 13

The prior art errors of a lens centered at A are of two types. one, oblique astigmatism due to the angle of line of sight a any from the optical axis and the other, a strong prismatic action which 'is equivalent to a prism at B of more than one prism dioptre, base out. This prism is in front of both eves so that the binocular imbalance is double this one dioptre or two prism dioptreswhich produces serious eye strain. The actual astigproximately one eighth of a dioptre. In the goggle of the invention these errors have been reduced to, less than one half of these values. At outer portions where monocular vision only can exist because of the nose, ctcl, the prismatic error is of no in'iportance as it cannot produce muscular imbalance. There is no strain between the two eyes, and consequent-ly this error can be much larger without any eye strain.

Referring to Fig. 1. R represents the center of rotation of the eye and the line RB represents the line of'direct vision ahead. The point B is to be made the optical center of the lens. The center of curvature O. of the'inner surface 3 ofthe lens 2 lies on the line BO which is normal to the surface 3 at B. The center of curvature 0 of the outer face 4 of the lens 2 lies on a line through the point B and the point 0 and this determines the optical axis of the lens.

In the lens indicated in Fig; 1 which is a cylindrical lens but just as well might be a spherical lens, the radius BO equals plus 58.89 millimeters and theradius OA equals minus 58.08 milimeters; the center thickness at the point BB equals 2.43 millimeters. The chord CF equals 77 millimeters and the chord CB equals 19.1 millimeters. The angle BLC equals 50 degrees and the distance BK equals 22.2 millimeters, this angle and distance constituting an average position of the lens as worn by various people and they will be varied with the major dimensions of the lens and the position of the optical axis to correspond. The circle of radius BK is the distance from the center of rotation of the eye to the cornea. D and E are additional points of the'lens defined by the chord BD equal 41.16 millimeters and chord BE equals 55.39 millimeters.

Calculation of the lens constructed as shown in Fig. 1 gives the. following figures:

2:2 Astigmatism Deviation Prism displacement .19 diopters D.G4 degrees prism diopters. .04 dlopters..- 0. 25 degrees. prism diopters.

+0. 33 degreesul +0. 73 degrees" +1. 00 degrees; 7 prism diopters. +1. 09 degrees. .9 prism diopters.

. (liopters... .30 diopters... 0.38 diopters l 1 0 4 0. 6 prism diopters. 1.3 prismdiopters. 1 1

It will be understood that the optical center does not have to be right at B. It might well be nearer G. Then the values of astigmatism and prism displacement at B would be reduced but then that at A would be increased, so it is well to obtain a good balance. The exact point where this balance is to be made is to be determined for the specific use of the device. From the foregoing data and tables it will be seen that this lens has sensibly plano power throughout and actual plano power at some 1ircdctermined point and yet has an optical axis (which connects lhc two centers of cur-vat lire) and consequent ly has an optical center where this optical axis pierces the lens. Also it is-clear that if these tivo curves are conceptric. there is no optical center. yet the lensh: "power.

At the point C the prism has its base towards A. At the point between A and B the base of the prism is reversed. The relative prism betwen the two eyes is twice as great as for one eye. There more prism at. the extreme znglc F but only monocular vision is obtained there. as the nose is in the way; hence there is no e vestrain. while on vision straight ahead on the line lt B there is only 0.4 prism dioptrcs. The calculations for obtaining astigmatism. deviation and prism displacement are well known to those skilled in the design of ophthalmic lenses.

Referring to the table. it will be seen that vision along the line 1 l" is very good, the astigmatism being only 0.0% dioptrcs. the deviation 0.25 degrcesand the prism displacement 0.4 prism dioptrcs- The vision along the line R-eA is also very good; all of which is in line of binocular vision.

7 In Fig. 2 the eyeball is designated by '1, the center of rotation of the eye at R, and the nose by 5. The lens 2 is held in the lens frames 6 which a re secured together by means of the bridge 7 which in the present instance is a chain 8 covered by a piece of rubber tubing 9. The lenses are held in place on the nose by means of the head bank 10 and'a soft flexible face engaging portion'li is'also secured to the frame 6 to make the lit of the frame snug against the face to keep out air,

dust. etc., and also to give a comfortable support to the frame.

It will be noted that the depth offthe frame; that is, the distance from the face contact to the outer surface of the lens, is very small. The shorter this distance the wider range of vision one has.

Referring to'Fig. 3. it will he noticed that the mechanical center A of the lens is some distance from the optical center B, the optical center B being located approximately at the center of the eye when the eye is looking straight forward.

The lenses 2 are ground to optical requirements described above. as shown in Fig. 1. They are then edged to shape. shown in Fig. 3, and secured. in the frames 6. care being taken that in locating the lenses. in the frames the optical center of the lens B falls approxicenter of the eye, as shown in characteristics snugly'so that when the goggle is in place on the face thelenses take tne positions shown in Fig. .3 as near as may be.-

From the foregoing description it will be seen that there has been devised an optical lens having an optical center at B in which astigmatism, deviation and prism displacement have beenconsidered and calculated so as to give the least possible oblique astigmatism and other optical errors and to produce a wide field of vision, particularly binocular vision without strain so that the eye in its movement may have the clearest possible vision which may be quickly obtained and without fatigue. It will also be clear that a lens of this kind is an optically designed lens designed and manufactured toobtain certain optical advantages which are not present and which cannot be obtained with the plain glass lenses hitherto in use. It will also be seen that the invention is one. particularly adapted for uses wherein accurate and 'quick vision must be obtained, such as for aviators where defective vision may readily have disastrous results. This is of particular importance to aviators at the present time where long "sustained flights are being made and the eye fatigue from an imperfect goggle becomes of first importance.

Having described. my invention, what I claim 1s: 1 y

1. An ophthalmic lens having surfaces and optical properties computed for a definite relationship to the-eye when in use and having substantially zero power along its optical axis with surfaces approximating the curve of the forehead, the chord connecting the nasal and temporal edges making an angle of less than seventy degrees-with the line of straight ahead vision, the optical center lying substan tially at a point directly in front. ofthe pupil of the eye "for straight ahead vision and the distance from the geometrical center to the temporal edge being more than one and a half times the distance from the point of straight ahead vision. to the nasal edge, the temporal edge being extended beyond and rearwardly of theexternal canthus of the eye;

2;. An ophthalmic lens having surfaces and optical properties computed for a definite re-. lat-ionship with the eye when in use and having' ciirved surfacesthe chord of which con- 'necting' the nasala-nd temporal edges forms anacute angle with the line of straight ahead vision and whose optical center lies substan tially. at a point directly in front of the eye for straight ahead visionand the temporal portion of which is extended to extend beyond and rearwardly of the external canthus of the eye. i

8. ,An ophthah nic lens having surfaces and;

optical properties computed for a definite relationship with the eye when in use whose horizontal cross section is "the same for all horizontal planes passing ther'ethrough being bounded by divergent curved lens sur faces and whose vertical cross sections on any vertical plane passing tl'ierethrough has allel bounding 'ace surfaces, the chord of the surfaces connecting the nasal and temporal edges forming an acute angle with the line of straight ahead vision, the power being subing different radii for its front and back, sur= faces, the centers of curvature of which are separated one from the other, its optical center being located at a point substantially directly in front of the eye for straight ahead vision and having its temporal side extended beyond and rearwardly of the external canthus and whose chord connecting the nasal and temporal edges makes an acute anglewith the line of straight ahead vision.

5. An ophthalmic lens having surfaces and optical properties computed for a definite relationship with the eye when in use and having its optical center lying between fifteen and thirty millimeters from the nasal edge and having a deviation in power along the optical axis of less than one-tenth diopter from ZBI'O: power and having its temporal side extended beyond and rearwardly of the external canthus of the eye and whose chord connecting the nasal and temporal edges makes an acute angle with the line of straight ahead vision. 6. An ophthalmic lens having surfaces and optical properties computed for a definite relationship with the eye when in use having curved surfaces and having its optical center approximately twenty millimeters from the nasal edge, a total horizontal length of apand substantially zero power along the optical 1 axis and which has a thickness along the optical axis of over one and a quarter millimeters. 7. An ophthalmic lens having surfaces and optical properties computed for a definite re lationship with the eye when in use, having curved surfaces and having 1ts optical center substantially midway between its ge0n1etricalcenter and the nasal edge, and whose dis tance from the geometrical center to the temporal edge is greater than one and a half tunes the distance from the point of straight ahead vision to the nasal edge and whose chord connecting the nasal and temporal edges makes an acute angle with the line of straight ahead vision and which has substantially-zero power along the optical axis and a thickness of over one and a quarter millimeters along the same axis.

8. An ophthalmic lens having surfaces and optical properties computed for a definite relationship with the eye when in use and having curved surfaces, the chord of which connecting the temporal and nasal edges forms an acute angle with the line of straight ahead vision and whose optical center lies substantially at apoint directly in front of the eye for straigl' t ahead vision and the distance from the geometrical center to the temporal edge is greater than one and a half times the distance from the point of straight ahead vision to the nasal edge.

9. An ophthalmic lens having surfaces and optical properties computed for a definite relationship with the eye when in use whose horizontal cross section is the same for all horizontal planes passing therethrough, being forming an acute angle with; the line of straight ahead vision, the-power being sub stantially zero along the opti al axis, theop tical center being located substantially at a point directly in front of the eye for straight ahead vision and the distance from the geometrical center to the temporal edge being greater than one and a half times the distance from the point of straightahead vision to the nasal edge.

' 10. An ophthalmic lens having surfaces and optical properties computedfor a definite relationship with the eye when in use and having different radii for its front and back surfaces, the centers of curvature of which are separated one from the other, its optical cen ter being located at a point substantially directly in front of the eye for straight ahead vision and the distance from the geometrical center to the temporal edge being greater than one and a half times the distance from the pointof straight ahead vision to the nasal edge.

' 11. An ophthalmic lens having surfaces and -which has substantially zero power along the optical axis and which has a thickness along said axis of over one and a quarter milhamsters and the dlstance from the geometrical center tothe temporal edge beinggreater than one and a half timesthe distance from the point of straight aheadyision to thenasal edge.

12. An ophthalmic lens having surfaces and optical properties computed for a definite relationship with the eyewhen in use,

edge being greater than one and a half times i the distance from the point of straight ahead vision to the nasal edge.

. 13. An ophthalmic lens and optical p'roptrties computed for a delinite relationship with the eye when in use having curved (.livergent surfaces the chord of which cr'mnecting the nasal and temporal edges makes an acute angle with the line of straight ahead vision, the height of which is approximately that of the ordinary prescription lens and the length approximately twice that of the ordinary prescription lens, the optical center lying approximately midway between the geometrical center and the nasal edge, the-power along the axis being substantially zero and the thickness on said axis being more than one and, a quarter millimeters. i

14:. An ophthalmic lens having surfaces and optical properties computed for a definite relationship with the eye when in use .and having curved divergent surfaces, the height being approximately forty-two milli-,

meters, the length approximately eighty-five millimeters, the optical center approximately twenty millimeters from the nasal edge, the power along the optical axis substantially zero and the thickness along said axis more than one and a quarter millimeters.

15. An ophthalmic lens having surfaces and optical properties" adapted for a definite relationship withthe eye when in use and having curved surfaces, the chord of which connecting the nasal and temporal edges formsan acute angle with the line of straight ahead'vision and whose optical center lies having surfaces llO at a point between the geometrical center and the nasal edge and the temporal portion of which is extendedbeyond'and rearwardly of the external canthus of the eye.

16. An ophthalmic lens having surfaces and optical properties adapted for a definite relationship with the eye when in use and having its optical center lying between its geometrical cent r and the nasal edge and having a power along the optical axis-of sub-e stantiallyzero power and having its temporal side extended beyond and rearwardly of the external canthus of the eye and whose chord connecting the nasal and temporal edges I makes an acute angle with straight ahea vision. I v 17 An ophthalmic lens having curved surfaces, the chord of which connecting the nasal and temporal edges forms an acute angle with the line of straight ahead vision-and whose optical center liesat a point between the point of straight ahead vision and the nasal edge and the power of which along the optical axis is substantially zero, and the thickness along the optical axis is in excess of two millimeters.

18. An ophthalmic lens having surfaces and optical properties adapted for a definite relationshi with the eyewhen in use and having di erent radii for its front and back surfaces, the centers of curvature of which are separated one from the other, its optical center being located at a point between its geometrical center and nasal edge and the distance from the geometrical center tot'he temporal edge being greaterthan one and one-half times the distance from the point of straight ahead vision tothe nasal edge. 19. An ophthalmic lens having curved surfaces, the chord of which connecting the nasal and temporal edges forms an acute angle with the line of straight ahead vision and whose optical centerlies at apoint between the point'of straight ahead vision and the nasal edge and the power of which'along the optical axis is substantially zero. In testimony whereof I have afiixed my signature. p

' EDGAR D. TILLYER. 

